Sight glass question


Jun 23, 2009
Columbia, SC
The only time I see water in my sight glass is when I backwash. Isn't the water supposed to be visible when the filter is operating in the regular mode. As a possibly related issue the PSI on my gauge isn't creeping up. Any info would be appreciated.


Well-known member
Feb 18, 2010
Houston, TX
I think the only time you should see water in the sight glass is when you backwash. Someone correct me if I'm wrong, it wouldn't surprise me.

Some people on here have noted they don't see a gradual increase in pressure, it just happens quickly when it does rise. Or, you could also need a new gauge. If you haven't replaced it in a year or two, you could just get a new one. They're cheap, so if in doubt, replace it.

Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
Water should only be visible in the sight glass when backwashing. If you see it in there any other time it either means the multiport valve is leaking or the backwash drain line isn't draining properly.

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